Battery thermal event detection system utilizing battery pack isolation monitoring

Abstract

A system for detecting cell failure within a battery pack based on variations in the measured electrical isolation resistance of the battery pack is provided. The system includes an electrical isolation resistance monitoring subsystem for monitoring the electrical isolation resistance of the battery pack; a system controller coupled to the isolation resistance monitoring subsystem that detects when the electrical isolation resistance falls below a preset value; and a cell failure response subsystem that performs a preset response upon receipt of a control signal from the system controller, where the control signal is transmitted when the electrical isolation resistance falls below the preset value. The system may include a secondary effect monitoring system, wherein the cell failure response subsystem performs the preset response when the electrical isolation resistance falls below the preset value and the secondary effect is detected by the secondary effect monitoring system.

What is claimed is: 
     
       1. A system for detecting cell failure within a battery pack, wherein the battery pack is comprised of a plurality of cells, the system comprising:
 an isolation resistance monitoring subsystem, wherein said isolation resistance monitoring subsystem monitors an electrical isolation resistance of said battery pack; 
 a secondary effect monitoring subsystem that detects a secondary effect indicative of said cell failure, said secondary effect comprising at least an increase in battery pack temperature; 
 a system controller coupled to said isolation resistance monitoring subsystem and to said secondary effect monitoring system, wherein said system controller detects when said electrical isolation resistance falls below a preset value, wherein said electrical isolation resistance falling below said preset value is indicative of said cell failure; and 
 a cell failure response subsystem coupled to said system controller, wherein said cell failure response subsystem performs a first preset response upon receipt of a first control signal from said system controller, said first control signal transmitted by said system controller when said electrical isolation resistance falls below said preset value, provided that said secondary effect is detected by said secondary effect monitoring system, and wherein said cell failure response subsystem performs a second preset response upon receipt of a second control signal from said system controller, said second control signal transmitted by said system controller when said electrical isolation resistance falls below said preset value, provided that said secondary effect is not detected by said secondary effect monitoring system. 
 
     
     
       2. The system of  claim 1 , wherein said secondary effect monitoring subsystem monitors the battery pack temperature, and wherein said secondary effect corresponds to said battery pack temperature exceeding a preset temperature. 
     
     
       3. The system of  claim 2 , wherein said secondary effect monitoring subsystem is comprised of at least one temperature sensor mounted within said battery pack. 
     
     
       4. The system of  claim 1 , wherein said plurality of cells is segregated into at least a first plurality of cells and a second plurality of cells, wherein said battery pack is comprised of an enclosure and at least one electrically conductive segment in electrical communication with said enclosure, and wherein said at least one electrically conductive segment is interposed between said first and second pluralities of cells. 
     
     
       5. The system of  claim 4 , wherein said at least one electrically conductive segment is comprised of a combination of an electrically insulating member and an electrically conductive element, said electrically conductive element in electrical communication with said enclosure. 
     
     
       6. The system of  claim 1 , wherein said battery pack is comprised of an enclosure and a plurality of electrically conductive segments in electrical communication with said enclosure, and wherein said plurality of electrically conductive segments segregate said plurality of cells into a plurality of cell groups, wherein each cell group includes multiple cells. 
     
     
       7. The system of  claim 6 , wherein said at least one electrically conductive segment is comprised of a combination of an electrically insulating member and an electrically conductive element, said electrically conductive element in electrical communication with said enclosure. 
     
     
       8. The system of  claim 1 , wherein said cell failure response subsystem further comprises a warning indicator, and wherein said preset response comprises activating said warning indicator. 
     
     
       9. The system of  claim 8 , wherein said warning indicator is comprised of an indicator light. 
     
     
       10. The system of  claim 8 , wherein said warning indicator is comprised of a sound generator. 
     
     
       11. The system of  claim 1 , wherein said cell failure response subsystem further comprises a battery load controller, and wherein said preset response comprises reducing an electrical load on said plurality of cells of said battery pack. 
     
     
       12. The system of  claim 1 , wherein said cell failure response subsystem further comprises a battery load controller, and wherein said preset response comprises minimizing an electrical load on said plurality of cells of said battery pack. 
     
     
       13. The system of  claim 1 , further comprising a battery pack cooling system coupled to said cell failure response subsystem, and wherein said preset response comprises increasing cooling applied to said battery pack by said battery pack cooling system. 
     
     
       14. The system of  claim 1 , wherein said cell failure response subsystem further comprises a fire containment subsystem coupled to said battery pack, and wherein said preset response comprises activating said fire containment system. 
     
     
       15. The system of  claim 1 , further comprising a memory coupled to said system controller, and wherein said preset response comprises recording date and time information corresponding to said electrical isolation resistance falling below said preset value within said memory. 
     
     
       16. The system of  claim 1 , further comprising a communication and notification subsystem coupled to said system controller, and wherein said preset response comprises transmitting a notification message via said communication and notification subsystem. 
     
     
       17. The system of  claim 1 , wherein said isolation resistance monitoring subsystem monitors said electrical isolation resistance of said battery pack at a frequency of at least once per second. 
     
     
       18. The system of  claim 1 , further comprising another secondary effect monitoring subsystem that monitors another secondary effect. 
     
     
       19. The system of  claim 18 , wherein the other secondary effect is determined by monitoring transmission of light through an optical fiber incorporated into the battery pack. 
     
     
       20. The system of  claim 18 , wherein the other secondary effect is determined by monitoring electrical continuity of a thermally interruptible electrical conductor incorporated into the battery pack. 
     
     
       21. The system of  claim 18 , wherein the other secondary effect is determined by monitoring voltage of an insulated conductor incorporated into the battery pack.